GET_DESCRIPTOR. It is probable that this request (with the descriptor type set to
Device) will be the first that will be received after USB reset. The host needs to
know the max packet length in use by the control endpoint and this information is
...

The host obtains descriptors from an attached device by sending various
standard control requests (GET_DESCRIPTOR requests) to the default endpoint.
Those requests specify the type of descriptor to retrieve. In response to ...